Designing thermal safety into process scale-up: Managing explosive decomposition and runaway risk

Abstract: Safe scale-up of chemical processes requires early identification and control of thermal instability hazards. This presentation outlines a practical framework for evaluating exothermic decomposition risks and establishing defensible thermal limits during process development and scale-up of new chemical processes. Exothermic reactions (ΔH < 0) present particular concern when the compound of interest can undergo self-accelerating thermal degradation. Heat released during decomposition increases reaction rate, creating the potential for runaway behavior. The risk is amplified at larger scales, where reduced heat transfer efficiency limits the system’s ability to dissipate energy. Rapid heat release, especially when accompanied by non-condensable gas formation, can produce dangerous pressure excursions and explosion hazards. Calorimetry is the primary tool for quantifying thermal risk. Techniques ranging from Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) to adiabatic methods such as Accelerating Rate Calorimetry (ARC) and Vent Sizing Package 2 (VSP2) provide insight into onset temperature, heat release, and runaway potential. A critical parameter in interpreting calorimetry data is the Φ (phi) factor, which accounts for the thermal inertia of the test cell. High Φ methods are valuable for rapid screening but require conservative safety margins, whereas low Φ (near-adiabatic) techniques more accurately simulate large-scale conditions. This talk will discuss how to interpret calorimetric data across Φ regimes, apply appropriate safety factors, and translate laboratory findings into safe maximum process temperatures. Emphasis will be placed on integrating thermal hazard assessment into early process development to prevent runaway events during scale-up and commercial manufacture.